Nike's Free technology is designed to provide you with all of the benefits of barefoot training, but with durable outsoles to protect the bottoms of your feet. This means that your feet will be able to move naturally as you run, jump, change directions, etc. This can strengthen the often neglected muscles in your feet, and lead to performance advantages over time. As for the Nike Free rating system, 0 represents barefoot training, while 10 represents performing in traditional footwear.